That is less than half of the rated CFM, and this fan has very good staticpressure as I recall. One thing I was thinking about is that the heatercore isn't working as well as it could. I JB welded the 5/8" barbs on it. And when I did it some JB weld fell down into the heatercore. However, I had the heatercore on it's back, and from what I could see it was just dropped on the the back of the tank, and didn't get in the way of any "channels." Maybe I'm wrong.
Here's the link to my 172mm fan specs! (4.2 m3/min = 148.323 ft3/min).
Also, I have the 5W rheostat from allelectronics.com, but I run it on full blast for the most part. Could the rheostat be dropping the voltage to the fan a little even though it's turned up all the way? Or do you think it's just a dust thing. I know right now there is some dust in there, but I thought I had cleaned it out resently when I took the readings. Also, I have the Antec (Chenming) Dragon case, so the front panel isn't resticting air flow much. And I did dremel out a complete opening for the heatercore in the sheet metal.
Maybe I will clean out the heatercore's fins and retake some readings. Good idea? Thanks for the help.